Comprehensive detection and some structural elucidation of disinfectant by-product (DBP) DNA adducts formed in vivo will be undertaken in this project. The analysis will rely on a combination of fluorescence post- labeling, capillary electrophoresis-laser induced fluorescence detection (CE-LIF), HPLC and mas spectroscopy (MS) techniques. CE-LIP detects nucleotide standards at the low amol level (same ultra-sensitivity as 32P- post-labeling). Tissue samples (furnished by NTP) from animals exposed to four DBP chemical (bromodichloromethane, sodium chlorate, 3- chloro-4-(dichloromethyl)-5-hydroxyl-2 (5H)-furanone and dibromoacetic acid) will be tested. Because the dye for adduct labeling has significant mass, the resulting dye-DNA adduct conjugates can be detected with high sensitivity (low fmol level) by matrix-assisted laser desorption ionization (MALDI)-MS. Both time-of-flight and Fourier transform MS instruments will be used, with the latter providing accurate mass and (MS)n measurements to enhance the partial structural elucidation of unknown DNA adducts to be discovered in this project. Comprehensive, definitive detection of DNA adducts in these exposed animals as proposed, with simultaneous monitoring of carcinogenicity, is a good, first step towards understanding the corresponding risk to humans from exposure to these chemicals. The ultra-sensitivity of CE-LIF makes it likely that the methodology will be useful, as needed, for the analysis of human samples in the future.